Various proposals have been made heretofore for specifically constructed drafting machines equipped with means for performing various drafting operations including precision measuring and plotting operations. Typical of these proposals are set forth in U.S. Pat. Nos. Rabe 2,112,113; Pascoe et al 3,166,844; Fausel 3,758,949; and Whetstone 3,956,588. Rabe poses modifying a drafting machine in a manner adapted for it to perform planimeter functions. The device has a main scale and a vernier scale both of which must be read, their readings combined, and then multiplied by a constant. This is a laborious and time consuming operation at best, and one or both scales can be misread and mistakes can occur in summing and multiplying them with a constant. Each of the other three proposals also involve a specially constructed drafting machine equipped with electrical connections between one of more sensors and remotely located readout device. No one of these devices has a motion sensor and signal generator in rolling contact with the drafting surface, nor a single sensor which is quickly and accurately positionable to measure linear movements selectively or angularly in X and Y directions, at the user's option.